This invention relates to an improved winding arrangement for the pole of a dynamoelectric machine, and in particular it relates to an improved edgewise wound winding arrangement suitable for the poles in a large dynamoelectric machine.
In a large dynamoelectric machine such as, for example, a synchronous machine, the rotor poles are usually wound with conductors of generally rectangular cross-section which may be wound edgewise and extend substantially from top to bottom of the pole. To provide curved corner regions, there is normally an end plate mounted at each end of the pole. Each end plate thus provides two curved corners. When such a conductor bends around a corner of the pole, there is a tendency of the conductor to leave a gap in the region where the conductor leaves the pole proper at a corner and begins to bend around the end plate. This is due to the inherent characteristics of the conductor including an inability to make sharp bends. There is also a tendency for the conductor to leave a gap in the region of the actual bend. In addition, because the outer edge of the conductor is stretched and the inner edge is compressed around the bend, the inner edge is upset, that is, the inner edge region is forced outwardly or becomes thicker. In order to reduce the gap in the region where the pole and the end plate abut, it is known to "taper" the pole laminations, that is, to reduce the laminations slightly in size and thereby to extend the bending region for the conductor. It is also known to insert filler strips in gaps left between the end plate and the conductor. It is sometimes necessary to increase the size of the end plate to carry the conductors if the gap between the conductors and the end plate is too great. Also, it is necessary to remove the upset at the inner edge of the bent conductor so that the coil formed will be compact and not distorted. This may be done by grinding, subsequent pressing, or a combination of both. No matter how it is done, the removal of the upset is time consuming and increases the labour costs.
Some low speed synchronous dynamoelectric machines do not have end plates. Instead, for example, corners may be machined on the pole itself, or the radius at the corner may be replaced by a bevel.
In summary, the inside radius of the bend is determined by the physical characteristics of the conductor. It would be desirable to have the conductor, for a given radius of bending, conform more closely to the pole and end plate. In addition, it would be very desirable to reduce the upset at the inner edge of the conductor so that the removal of the upset would be less time consuming and more efficient.